Fixation device with magnesium core

Abstract

A fixation device comprises a biodegradable inner core extending along a longitudinal axis from a distal tip to a proximal end in combination with a sleeve surrounding the core along a portion of a length thereof and comprising a thermoplastic polymer formed of a material which softens and expands into surrounding bone tissue when activated by an energy source.

What is claimed is: 
     
       1. A fixation device, comprising:
 a biodegradable inner core extending along a longitudinal axis, such that the inner core defines a tapered distal tip spaced from a proximal end along the longitudinal axis, wherein the tapered distal tip is configured to break a cortical portion of a bone when the fixation device is inserted into the bone along the longitudinal axis; and 
 a sleeve defining a proximal end and a distal end opposite the proximal end, such that in an assembled configuration, the sleeve surrounds the core along a portion of a length thereof such that the tapered distal tip of the biodegradable inner core extends distally past the distal end of the sleeve, the sleeve comprising a thermoplastic polymer formed of a material which softens and expands into surrounding bone tissue when activated by an energy source, 
 wherein the fixation device is configured to be inserted into the bone in the assembled configuration. 
 
     
     
       2. The fixation device according to  claim 1 , wherein the biodegradable inner core is a biodegradable metallic inner core. 
     
     
       3. The fixation device according to  claim 2 , wherein the core comprises one of magnesium and a magnesium alloy. 
     
     
       4. The fixation device according to  claim 2 , wherein the core comprises an iron alloy. 
     
     
       5. The fixation device according to  claim 2 , wherein the core comprises a bulk metal glass. 
     
     
       6. The fixation device according to  claim 5 , wherein the bulk metal glass is of a MgCaZn type. 
     
     
       7. The fixation device according to  claim 5 , wherein the bulk metal glass is one of Mg 53 Zn 32 Ca 5 , Mg 60 Zn 35 Ca 5 , Mg 32 Zn 5 Ca, or Mg 35 Zn 5 Ca. 
     
     
       8. The fixation device according to  claim 1 , wherein the core comprises a non-bulk metal glass. 
     
     
       9. The fixation device according to  claim 8 , wherein the non-bulk metal glass is one of Mg 5 ZnZr, Mg 3 AlZn, MgAl 9 Zn, Mg 3 Al 0.4 Mn, Mg 6 Al 0.2 Zn, MgYRe (Re=Rare Earth), Mg 4 Zn 1.7 Ce 0.6 Zr. 
     
     
       10. The fixation device according to  claim 8 , wherein the non-bulk metal glass has a surface treated by one of hard anodization and micro-arc oxidation (MAO). 
     
     
       11. The fixation device according to  claim 1 , wherein the thermoplastic polymer is biodegradable. 
     
     
       12. The fixation device according to  claim 1 , wherein the core is hollow. 
     
     
       13. The fixation device according to  claim 1 , wherein the sleeve comprises one of metallic and organic dye particles that diffract light. 
     
     
       14. The fixation device according to  claim 1 , further comprising a suture attached to the fixation device. 
     
     
       15. The fixation device according to  claim 14 , further comprising an end cap attachable to the proximal end of the inner core, the end cap including a through hole extending transversely therethrough to accommodate the suture therein. 
     
     
       16. The fixation device according to  claim 14 , wherein the inner core includes a hook at the proximal end thereof to attach the suture to the fixation device. 
     
     
       17. The fixation device according to  claim 1 , wherein the inner core includes a through bore extending transversely therethrough to accommodate a suture therein. 
     
     
       18. The fixation device according to  claim 1 , wherein the sleeve includes a through opening extending transversely therethrough, the through opening aligned with and in communication with a through bore of the inner core. 
     
     
       19. The fixation device according to  claim 1 , wherein the fixation device is one of a bone anchor or a bone screw. 
     
     
       20. The fixation device according to  claim 1 , wherein the energy source is one of a radiation device, a laser, a heat source, an electromagnetic field, a light source, or an ultrasound device. 
     
     
       21. A method for inserting a fixation device into a bone, the fixation device including a sleeve defining a proximal opening and a distal opening and comprising a thermoplastic polymer, and a biodegradable inner core surrounded by the sleeve along a portion of a length of the biodegradable inner core, the method comprising the steps of:
 a) pre-assembling the fixation device to form a pre-assembled fixation device by inserting the biodegradable inner core through the sleeve along a first direction such that a distal tip of the biodegradable inner core is spaced distally from the distal opening of the sleeve; 
 b) driving a distal tip of the biodegradable inner core of the pre-assembled fixation device into a target portion of the bone along the first direction such that the distal tip of the biodegradable inner core breaks a cortical portion of the bone so as to create a point of entry for the pre-assembled fixation device, wherein when the pre-assembled fixation device has been fully inserted, the sleeve and the biodegradable inner core are disposed in the target portion; and 
 c) applying an activation energy to the sleeve so as to soften the thermoplastic polymer of the sleeve, thereby causing the sleeve to expand into the target portion of the bone that surrounds the sleeve, and fixing the fixation device therein. 
 
     
     
       22. The method of  claim 21 , wherein the fixation device is one of a bone anchor or a bone screw. 
     
     
       23. The method of  claim 21 , wherein the applying step comprises applying the activation energy using one of a radiation device, a laser, a heat source, an electromagnetic field, a light source, or an ultrasound. 
     
     
       24. The method of  claim 21  further comprising the step of passing a suture through a through bore in the biodegradable inner core. 
     
     
       25. The method of  claim 24 , wherein the passing step further comprises passing the suture through a corresponding through opening in the sleeve. 
     
     
       26. The method of  claim 24 , wherein the passing step further comprises aligning the through bore of the biodegradable inner core with the corresponding through opening in the sleeve prior to passing the suture through the through bore and the through opening. 
     
     
       27. The method of  claim 24 , wherein the passing step is performed prior to the driving step.